如何将get-parameter传递给jsf中的backing bean? [英] How to pass get-parameter to backing bean in jsf?

问题描述

我有一个名称为 controller 的get参数.当我尝试将其(使用 propertyChangeListener )传递到支持bean时，我得到的是 null 而不是该参数的实际值:

I have a get-parameter with name controller. When I try to pass it (with propertyChangeListener) to my backing bean I get null instead of the real value of that parameter:

<h:commandButton value="#{msg['mail.send']}" styleClass="mailbutton" action="#{mailSender.sendMail}">
   <f:setPropertyActionListener target="#{mailSender.controllerName}" value="{#param.controller}"/>
</h:commandButton>

所以，我有两个问题:

1. 用get-parameter值设置bean属性的正确方法是什么?实际上，我已经从 ExternalContext#getRequestParam 中获取了值，但是也许还有其他解决方案.
2. 一个更有趣的问题:为什么propertyActionListener在这里不起作用?它实际上是做什么的?(同样，我对此有一些想法，但是阅读更全面的解释会很不错).

1. What is the proper way to set bean property with a get-parameter value? Actually, I've already get the value from ExternalContext#getRequestParam but maybe there are some other solutions.
2. More interesting question: why propertyActionListener didn't work here? What does it do actually? (again I have some thoughts about it but it would be nice to read more comprehensive explanations).

推荐答案

首先， h:commandButton 触发 POST 请求，而不是 GET 请求.要触发 GET 请求，您需要 h:outputLink .要设置 GET 参数，您需要 f:param .要将其设置为bean属性，请将其定义为 faces-config.xml 中的< managed-property> ，其值为#{param.name}.在此处中可以找到更多的提示和代码示例.

First, a h:commandButton fires a POST request, not a GET request. To fire a GET request, you need h:outputLink. To set a GET parameter, you need f:param. To set it as a bean property, define it as <managed-property> in faces-config.xml with a value of #{param.name}. More hints and code examples can be found here.

第二，您的代码无效. f:setPropertyActionListener 值应为#{param.controller} .为了使其正常工作，在最初的请求期间，#{param.controller} 应该已经在那里.它不会像您期望的那样在后续请求中自动设置值.为此，您需要< h:inputHidden value =#{mailSender.controllerName}"/> .

Second, your code is invalid. The f:setPropertyActionListener value should have been #{param.controller}. And to get it to work, the #{param.controller} should already be there during the initial request. It does not automagically set the value in the subsequent request as you seem to expect. For that you need <h:inputHidden value="#{mailSender.controllerName}"/> instead.

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